A crystal oscillator is an important device in integrated circuit. The crystal oscillator generates regular oscillations in crystal material (common material comprise quartz and germanium etc) chiefly through active drive or passive reactance network. The accuracy of oscillations frequency is unbeatable and the oscillations are capable of being clock signals. The frequency of the clock signals is multiplied or divided through a frequency generator for further obtaining a conventional counting pulse and a clock cycle etc.
FIG. 1 schematically illustrates a crystal oscillator in prior art. The crystal oscillator comprises an insulation shell 2, an oscillating crystal 1, supporting columns and a drive plate 3. A closed cavity is surrounded by the insulation shell 2. The oscillating crystal 1 is located in the closed cavity. Opposite terminals of the oscillating crystal 1 are supported by the supporting columns, and thus the oscillating crystal 1 is suspended in the closed cavity. The supporting columns may be an anode and a cathode which are connected with the oscillating crystal 1. The drive plate 3 is arranged on one side of oscillating crystal 1 in the closed cavity for inducing the oscillating crystal 1 to generate oscillations. While working, the oscillating crystal 1 is electrified through the anode and the cathode, and then drive plate 3 is electrified to form electric field in the closed cavity. Thus subject to the electric field, the oscillating crystal 1 generates regular oscillations and outputs clock signals with fixed frequency through the anode and the cathode.
Current crystal oscillators are encapsulated as discrete devices and are arranged outside a semiconductor chip, which is not beneficial to reduce the size of integrated circuit. As density of circuit element increases and area of circuit restricts, dimension of crystal oscillators is required higher and higher. Although MEMS (Micro-Electro-Mechanical Systems, MEMS) technology is developed and mechanical electrical devices with micron grade and submicron grade have been fabricated, current semiconductor chip manufacturing process bases on CMOS process, and crystal oscillators and semiconductor chip are difficult to be fabricated uniformly only depending on MEMS technology. Therefore, a crystal oscillator and manufacturing method of the crystal oscillator which base on CMOS process is urgently demanded.